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Commit682ce91

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Allow parallel query for prepared statements with generic plans.
This was always intended to work, but due to an oversight inmax_parallel_hazard_walker, it didn't. In testing, we missed thefact that it was only working for custom plans, where the parametervalue has been substituted for the parameter itself early enoughthat everything worked. In a generic plan, the Param node survivesand must be treated as parallel-safe. SerializeParamList providesfor the transmission of parameter values to workers.Amit Kapila with help from Kuntal Ghosh. Some changes by me.Discussion:http://postgr.es/m/CAA4eK1+_BuZrmVCeua5Eqnm4Co9DAXdM5HPAOE2J19ePbR912Q@mail.gmail.com
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4 files changed

+37
-7
lines changed

4 files changed

+37
-7
lines changed

‎src/backend/optimizer/util/clauses.c

Lines changed: 6 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1223,13 +1223,17 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
12231223

12241224
/*
12251225
* We can't pass Params to workers at the moment either, so they are also
1226-
* parallel-restricted, unless they are PARAM_EXEC Params listed in
1227-
* safe_param_ids, meaning they could be generated within the worker.
1226+
* parallel-restricted, unless they are PARAM_EXTERN Params or are
1227+
* PARAM_EXEC Params listed in safe_param_ids, meaning they could be
1228+
* generated within the worker.
12281229
*/
12291230
elseif (IsA(node,Param))
12301231
{
12311232
Param*param= (Param*)node;
12321233

1234+
if (param->paramkind==PARAM_EXTERN)
1235+
return false;
1236+
12331237
if (param->paramkind!=PARAM_EXEC||
12341238
!list_member_int(context->safe_param_ids,param->paramid))
12351239
{

‎src/pl/plpgsql/src/pl_exec.c

Lines changed: 5 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -6588,8 +6588,8 @@ exec_save_simple_expr(PLpgSQL_expr *expr, CachedPlan *cplan)
65886588
* force_parallel_mode is on, the planner might've stuck a Gather node
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* atop that. The simplest way to deal with this is to look through the
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* Gather node. The Gather node's tlist would normally contain a Var
6591-
* referencing the child node's output ...butsetrefs.c might alsohave
6592-
*copieda Const as-is.
6591+
* referencing the child node's output,butit could alsobe a Param, or
6592+
*it could bea Const that setrefs.c copied as-is.
65936593
*/
65946594
plan=stmt->planTree;
65956595
for (;;)
@@ -6616,9 +6616,9 @@ exec_save_simple_expr(PLpgSQL_expr *expr, CachedPlan *cplan)
66166616
/* If setrefs.c copied up a Const, no need to look further */
66176617
if (IsA(tle_expr,Const))
66186618
break;
6619-
/* Otherwise, it better be an outer Var */
6620-
Assert(IsA(tle_expr,Var));
6621-
Assert(((Var*)tle_expr)->varno==OUTER_VAR);
6619+
/* Otherwise, ithadbetter be a Param or an outer Var */
6620+
Assert(IsA(tle_expr,Param)|| (IsA(tle_expr,Var)&&
6621+
((Var*)tle_expr)->varno==OUTER_VAR));
66226622
/* Descend to the child node */
66236623
plan=plan->lefttree;
66246624
}

‎src/test/regress/expected/select_parallel.out

Lines changed: 20 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -101,6 +101,26 @@ explain (costs off)
101101
-> Parallel Index Only Scan using tenk1_unique1 on tenk1
102102
(5 rows)
103103

104+
-- test prepared statement
105+
prepare tenk1_count(integer) As select count((unique1)) from tenk1 where hundred > $1;
106+
explain (costs off) execute tenk1_count(1);
107+
QUERY PLAN
108+
----------------------------------------------
109+
Finalize Aggregate
110+
-> Gather
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Workers Planned: 4
112+
-> Partial Aggregate
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-> Parallel Seq Scan on tenk1
114+
Filter: (hundred > 1)
115+
(6 rows)
116+
117+
execute tenk1_count(1);
118+
count
119+
-------
120+
9800
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(1 row)
122+
123+
deallocate tenk1_count;
104124
-- test parallel plans for queries containing un-correlated subplans.
105125
alter table tenk2 set (parallel_workers = 0);
106126
explain (costs off)

‎src/test/regress/sql/select_parallel.sql

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -39,6 +39,12 @@ explain (costs off)
3939
selectsum(parallel_restricted(unique1))from tenk1
4040
group by(parallel_restricted(unique1));
4141

42+
-- test prepared statement
43+
prepare tenk1_count(integer)Asselectcount((unique1))from tenk1where hundred> $1;
44+
explain (costs off) execute tenk1_count(1);
45+
execute tenk1_count(1);
46+
deallocate tenk1_count;
47+
4248
-- test parallel plans for queries containing un-correlated subplans.
4349
altertable tenk2set (parallel_workers=0);
4450
explain (costs off)

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